1. Field of the Invention
The present invention relates to a heart stimulation apparatus for intracardial stimulation of heart tissue and/or sensing heart signals of the type having an electrode lead with an electrode head at the distal end thereof, the electrode head having at least first and second conductive surfaces for stimulating heart tissue and/or sensing heart signals respective connected to first and second separate conductors, the conductive surfaces being insulated from each other, and a stimulation pulse generator and/or a heart signal detector and a switch for connecting one conductive surface, or a plurality of the conductive surfaces, to the stimulation pulse generator and/or the detector in any desired manner.
2. Description of the Prior Art
A heart stimulation apparatus is disclosed in U.S. Pat. No. 4,628,934 in which an electrode lead can be provided with a plurality of independently connectable electrodes. The electrodes include a plurality of ring electrodes installed relatively far apart, and a conductive electrode tip. A switching stage is provided for connecting the electrodes in selected combinations to the pacemaker circuitry in a manner determined by a physician to be best suited for a given pacing function. Each electrode is individually tested to determine its capture threshold.
Another electrode device is known from U.S. Pat. No. 3,911,928 wherein a plurality of relatively small conductive surfaces are arrayed on the head of the electrode device in order to reduce the threshold value and also to reduce thus energy consumption. All the conductive surfaces on the head of this electrode device are connected to the same conductor. This can result in needlessly large energy consumption, since some of the conductive surfaces are not in contact with heart tissue for stimulation.
U.S. Pat. No. 4,760,852 describes a pacemaker electrode with a plurality of relatively large conductive surfaces connected to the same conductor disposed at a distal end of the electrode device.